The present invention relates to devices ror measuring temperature and in particular to a device which utilizes the variation in the index of refraction with temperature of various materials and a light spectrum refracted therethrough and reflected thereby to provide a device which can sense temperature to a high degree of accuracy and which enables transmission of the signal containing the temperature intelligence via fiber optic conductors.
Various devices are presently known for sensing and transmitting signals indicative of temperature. These devices include thermocouples, platinum resistance thermometers, Bourdon tubes, and the like to mention a few. When such devices are utilized in conjunction with electronic controls, the controls typically being located remotely from the sensed temperature, it is common to transmit the data by means of electrical conductors. Such conductors are subject to electricl noise, EMI, EMP, and other induced electrical effects. Such devices typically produce data in analog format such that the data must subsequently be converted from analog to digital format for processing in contemporary computer control circuits. Many of these devices which exhibit high degrees of accuracy are correspondingly fragile and subject to destruction or inaccurate operation in a hostile environment.
There therefore exists a need for a temperature sensing device operable in hostile environments which is capable of producing a highly accurate temperature reading, capable of transmitting a signal corresponding to the temperature reading by means resistant to electrical noise, and to provide such a device which is very rugged, reasonably inexpensive to produce, and which is small in size.
Broadly, the present invention is an optical spectral temperature sensor which comprises means for generating a beam of radiant energy of predetermined spectral bandwidth, a first optically transparent medium having a first index of refraction and optical dispersing means for generating a spectral dispersion of said beam as a function of wavelength into said first medium. A second optical medium having an index of refraction variable as a function of temperature is disposed contiguous to the first medium in a position to intercept a portion of the spectral dispersion and reflect and diffract portions of the spectrum at angles greater than and less than the critical angle of incidence, respectively, as a function of the difference of the indices of refraction of the first and said second optically transparent media. Means are provided for sensing the displacement of the spectral dispersion variably diffracted as a function of temperature by said optically transparent media.
It is therefore an object of the invention to provide a temperature sensor utilizing an optically transparent medium having an index of refraction variable as a function of temperature to variably refract and reflect portions of a spectrum of radiant energy as a function of temperature.
Another object of the invention is to provide such a temperature sensor utilizing a dispersion of a beam of light with a predetermined bandwidth and the variation in the indices of refraction of optically transparent media as a function of temperature to produce a variably refracted optical spectrum as a function of temperature.
Yet another object of the invention is to provide such a temperature sensor made of materials which permit the sensor to operate in high temperature environments.
Still another object of the invention is to produce such an optical temperature sensor which is stable and produces a temperature reading to a high degree of accuracy.
Another object of the invention is to produce an optical temperature sensor which produces a digitally compatible output signal.
Yet another object of the invention is to produce a temperature sensor which permits interconnection thereof with an electronic device by means of optical fiber conductors.
Still another object of the invention is to produce an optical temperature sensor which operates without an external power source and which is small in size and rugged in construction.